EARLY PALEOGENE CRABS (CRUSTACEA: BRACHYURA) AND SEDIMENTOLOGY OF THE KAMBÜHEL FORMATION, SOUTHERN AUSTRIA

Fossil Brachyura from the Paleocene Kambühel Formation, Austria, have been largely unidentified. Although the K-T boundary has been widely studied, many questions about the fate of crabs remain. Thus, the significance of this mass extinction event on ecosystems and crabs of the Kambühel Formation is being investigated. Hypotheses tested are that all the brachyuran genera and species present in the Kambühel Formation, which are associated with shallow, reef paleoenvironments, arose after the K-T boundary during the Paleogene, and therefore are not representatives of genera or species that survived across the boundary.

Due to the small size of the specimens, measurements were taken with digital calipers under microscope, and pictures were also taken under the microscope. Digital reconstructions of specimens were created for purposes of identification. Acetate peels and thin sections permit study of the Kambühel Formation’s paleoecology. The fossils observed in thin section indicate that Brachyura lived in shallow marine, reef environments associated with red algae and coral. Of the specimens already examined, there are two possible new species of Dromiopsis, a possibly new genus of Goniodromitidae, and a species of Titanocarcinus. One specimen of Jakobsenius is incomplete and cannot be identified to species. Many of the specimens identified as Titanocarcinus kambuehelensis will be verified. Gastropods, algae, coral, bryozoans, and decapods were observed in associated matrix under thin section. Preliminary results show that the crab specimens may belong to new species that arose after the K-T boundary. The crab specimens are similar to Danian specimens from Fakse Quarry, Denmark. In comparison, the Fakse fossils are larger, in better condition, and surrounded by unbedded limestone deposited as deep-water bryozoan and azooxanthellate coral mounds. Specimens from the Kambühel Formation have yet to be identified as genera or species that have survived the K-T boundary, and so far support the hypothesis. This research is significant in understanding how species respond and recover from extinctions, to inform our response to ongoing environmental crises and human-driven extinctions.